高力ボルト引張接合に関する研究 : その一 ボルト初張力の影響

Abstract

The influence of initial bolt tension upon the mechanical characteristics of bolted connections are investigated by using simple specimens, of which bolts have different initial tension, and idealized model. The main results are as follows. 1) The separation load is in proportion to initial bolt tenssion without regard to the magnitude of initial bolt tension. 2) The ultimate strength of the bolted connection is constant regardless of the magnitude of initial bolt tension. 3) In order to keep the behavior of bolted connection in reversible condition, the limit of repeated loads is restricted under the elastic proof load of bolts. when the connection is subjected to the load, which gets beyond the elastic proof load of the bolts, the reduction of residual bolt tension, separation load and the rigidity of the connection take flace after unloadindg. The degree of those reduction changes according to the total deformation of the connection after separation. So the degree of those reduction is small, when bolts have large initial tension. Judging from the general test results, the magnitude of initial bolt tension has great influence upon the mechanical characteristics of bolted connection. So initial bolt tension is recommended to be large, but there is no advantage, when the bolt are stressed in plastic range. Finally the recommended initial bolt tension is as large as the bolt yield load.